Graphic of a Non-rotating Planet world building project, decided to go for the 'Fallen Colony' ideas to populate, but of course adding my own twists .

If you have trouble viewing it I'd recommend opening it in a new tab. Be sure to read all the information in the graphic, if you have trouble reading it there here it is again:

The Climate of Throl

Like any tidally locked world, by far the greatest feature of the Throl climate cycle is the dayside/nightside dichotomy, with a tremendous thermal load at the sub solar point and a chill at the antipode, and a more liveable annulus at the terminator. The amount of heat Throl receives is low enough that convection could not break the permanent icecap formed at the antipode, and the absorption of the planets water inventory during its formation prevented seas and permanent storms from developing on the dayside. This is quite advantageous for human occupation, for if the icecaps were liquid only the highest mountains would be free of the resultant ocean.

The second order factor on the climate comes from Throl’s small size (68% of Terra’s Radius), high gravity for that size (0.93 g), and short orbit (a mere 0.23 AU from its orange dwarf primary). These combine to bias the atmospheric motion in a direction opposite to the orbital path (since air flowing backwards is ‘lighter’ as the planet moves through space). Due to the massively more energetic nature of the dayside atmosphere its bias quite overpowers the nightsides bias and creates a global circulation from west to east as shown in the diagram. Whilst twilights on both sides feature high hot air flowing into the night and lower cold air flowing back, on the eastern edge the hot air is much more dominant – leading to dry warm winds deep into the night with only light clouds and fogs moving back, whilst on the western edge the hot air is forced down and great masses of rain and cold clouds break off the icecap and move back onto the dayside.

The differences in geography of the east and western zones (called by the Throl inhabitants the Windside and Rainside respectively) only exacerbates these tendencies, with the high mountains of the Rainside capturing and cooling the air into clouds and the flat plains of the Windside letting the winds and fogs run far. The biospheric water of the Rainside comes from mountain fed rivers (often laced with poisons from Throls metal rich interior), whilst the Lakes of the Windside are fed directly from the margin of the antipodal ice.With these grand features in place, the climate of Throl is very stable with no seasonality, and the combined libration effects are small (Grombrid will appear to move about ten degrees up and down in the sky over the course of the sixty Terra-day orbit, widening the twilight zones. This creates hundreds of microclimate pockets that endure for millions of years, and drove incredible speciation of the native flora and fauna.

Biology of Throl

Most of the original biosphere has been stamped out by human terraforming efforts except in the twilight reaches of the Windside and certain Rainside valley’s. The flora was split into two main classes, one photosynthesising using a combination of a retinal-analogue and an oxygen producing purple and giving rise to purple coloured vegetation, the second using a selenium based photopigment and giving rise to vegetation with jet black leaves.

The Purple plants took a low moss and lichen like character due to a poor metabolic efficiency, and have been completely outcompeted by the more efficient Terran Green plants all throughout the Dayside. They are more effective at extracting energy from Grombrid’s dim orange rays refracting around the terminator however, and thus remain on the vast plains of the Windsides deep night. It is due to the plants employment of Bioluminescence to attract pollinators that the name of the region – “Ghost Plains” is derived.

The Black vegetation takes a coiling character like immensely tall feathery bamboo and is extremely vigorous, effortlessly displacing other forms of plant life with an incredible growth rate and an extremely poisonous character. However it is restricted to soils that contain the necessary metals for its biochemistry, and forms isolated groves around the planet that the human inhabitants tend to just leave be.

Both purple and black vegetation had an attendant animal ecology, both which were pushed back by the arrival of terran organisms, though some have managed to adapt to new regions. It is theorised that during a warmer epoch in the planets history a circular sea covered most of the twilight annulus and acted as a cradle for life before suddenly and rapidly drying out. This disaster was only survived by a few species, making up a total of 7 animal phyla (compared to Terra’s 35). Keratinised worms analogous to earth Nematodes do most of the ecological basic duties along with four other types of worms (the largest worms being the top predators in the lakes via use of long serpentine bauplans and powerful neurotoxins).

The large land animals come in only two types; the first the faux-arthropods being armoured in chitin like their terrain equivalents, but differing in having a closed circulatory system that is extremely compartmentalised by segment, each often being able to survive independently. The largest and most archetypical example is the Metapede order, reaching up to ten kg in weight and famed for their hundreds of legs, quartets of which can detach from the main body to search for food or mates. Some of the faux-arthropods can regulate their internal temperature and it is these which provide most of the native flying animals, with specialised rear segments sprouting eight panel like wings and bearing aloft creatures that range from milligrams to a kilogram.

The second major land animal phylum is the Rotizoa analogous to the Chordates of Terra. Instead of a notocord ventral to the gut, a ring shaped supporting structure circling the rear of the gut acts as the defining feature of this phylum. Forward of this ring a head containing the mouth and sensory organs projects (many species have ‘false’ heads with respiratory openings, specialised senses and tools produced by duplicating the main head during development), whilst to the rear an odd number of motor tentacles extend. In land dwelling examples the body and motor limbs are strengthened with semi-mineralised cartilage and an annular brain develops, whilst the heads are armoured with cartilage and keratin skulls and trefoil jaws. Warm blooded orders are thickly and fluffily furred with colours that appear metallic thanks to use of Dyck textures. Lacking true bones the largest species rarely reach 40 kg, but the use of hydraulic pipes in the motor tentacles and neck make them surprising strong for their size. Large species of this phylum are restricted to the Black groves in modern Throl, though squirrel-like species have made the transition to Terran forests quiet well, and are often kept as pets by the Human inhabitants.

In addition to normal terran species, a number of engineered species survived the Conflict. The largest in terms of number are the reindeer and cameloids of the Ghost Plains, altered to be able to consume Purple vegetation, survive the cold and dark plus produce better meat and hair products. Specialised Destrier and other massively engineered riding beasts, and intelligence augmented parrots, parrot-eagles, and dogs are found in all human societies that don’t find those things philosophically objectionable.

Peoples and cultures of Throl

Human Strains

Optimates

Optimate blood is the gift to those descended from the fashionable wealthy of Terra, inhumanly beautiful, tall, slender, and graceful, in addition to a host of alterations to the constitution and mind to cement their position as the elite. However after the Conflict some shortcomings of these developments became clear - in the raw environment the increased metabolic needs and extended infancy of the Optimate is greater than the net lifetime calories which can be produced by their individual labour as a hunter-gatherer or agriculturalist. They thus had to position themselves at the centre of more baseline societies, and appropriate their neighbours surplus by force or in exchange for services. Though immune to disease the difficulties of Optimate gestation in the absence of advanced medical technology gives rise to a slower rate of increase. The amount of Optimate blood smoothly transitions from a complete example down to baseline human, and the Senatorial and Lesser Clans closely monitor the gradations between themselves and the masses they rule. Despite their propaganda to the contrary the general greater level of intellect of the Optimates is due to access to educational resources, as the original engineers found quantifying and increasing raw intelligence very difficult, instead focusing on improving defined modules of brain structure, like memory and language facility.

Gifted

Many other alterations were enacted by the pre-Conflict population on their children, and echoes of these improvements still ring in the masses. To avoid problems caused by recombination, the genotype alterations included explicit error monitoring genetic modules, and thus an individual only displays a Gifted phenotype if they have all the appropriate alleles and extra genes. This causes Gifts to spring up semi-randomly and not be strongly hereditable (though some families have higher than average instances of a particular type, and certain organisations promote certain traits in their members - such as spatial awareness in the Sky Guild). Gifts run the gamut of physical, aesthetic, entertainment, mental, and esoteric changes. The most common Gift, occurring in about 7% of the Rainside population, is an increase in longevity of up to triple the normal lifespan. The Optimates own error protections prevent the more extreme gifts from manifesting in tandem with Optimate phenotypes.

Biseaorg

One of the more esoteric gifts is the ability to interface with ancient self-repairing biomechanical devices of various types, becoming a Biseaorg on a temporary or permanent basis and wielding great power (though the devices draw on the users own metabolism as well as sunlight). Due to the lack of common protocols, each bloodline is only compatible with certain families of devices (produced by differing pre conflict companies). In the absence of exposure to a device, someone with Biseaorg blood might go their whole life unaware of their capability, beyond knowing they tend to get sick a lot (since the machine connection requires a much less hostile immune system than the baseline average). Many Senatorial leaders go out of their way to secure and hide Devices in their vaults as a threat to their power.

Silverbloods

The closest to a new species amongst the humans of Throl, the Silverbloods combination of adaptions were very highly selected for in some of the Rainside environments. Unlike the Optimate and Gifted, these were specifically induced for life on Throl. The two biggest changes are to the eyes and liver. The eyes have a tapetum lucidum, wider pupils, polarizing filters, and a set of ultralarge cone receptors (the first two shared with the Nighteyes) together enabling colour night vision even under the clouds of the twilight. The liver is four times the size of a baseline human and multilobed, this is to enable the novel abilities of heavy metal sequestration against the often poisonous Rainside rivers, production of most necessary vitamins autonomously, and greatly enhanced internal heat production. The chelated metals are dumped in the skin cells of the lower arms and legs to be shed, giving them a mouldy metallic appearance. The incredible advantage of these changes in some locations coupled with animosity from the more normal populations has driven the Silverbloods into ghetto petty realms. In addition natural selection in these environments and a small population size has made them very pale and robustly built.

Nighteyes

Although occurring in the Rainside as a Gift, the Nighteyes package of changes is so prevalent amongst the population of the Windside as to be considered a strain in its own right. Like the Silverbloods the eye has been modified with vast pupils and a tapetum lucidum, but things have been taken further by enlarging the entire eye by 50%, partially enabled with larger eye sockets but mainly by decreasing the muscle mass devoted to eye movement. Unlike with the silvereyes ultralarge cones were not included, instead favouring an increased number of rods (cone cells and colour perception were even decreased in number). In tandem with these changes the neck is more flexible and the facial bone structure more delicate and sharp. Nighteyes make up a near 4/5ths of the Ghost Plains nomads. Increased ability to metabolise the poisons of Throl's native Purple and Black vegetation is even more common amongst the nomads and many consider it linked with the Nighteyes adaption, but the two are actually inherited separately. Many Nomads who inherit the former but not the latter find themselves having to leave the plains or face liver poisoning by their twenties, forming an underclass in the Redspire Forge Towns.

Major Societies

The Administration

The Administration is a loose organisation that claims direct descent and legitimacy from the old colonial government and to represent the humans of Throl. In practice is a dominated by the great Senatorial families who use their wealth, power, and longevity to pack the Senate, rule like lords in their own land and dismantle other organs of the government (an executive Premier has not been elected in six hundred years for example). The only remaining locus of power outside the 14 Great and 70 Lessor Senatorial Families is the Commercial Court, as even the Optimate Lords need someone to arbitrate their contracts. Even a baseline can rise high in the Court, and there are many stories of heroic Adventuring Lawyers travelling the countryside and righting wrongs. The control the Senatorials force on what they own varies wildly by place and family – on the Arshwater lower class individuals enjoy probably more liberty than any of the independent republics, whilst those in the Vale of Frost are effectively serfs. Each Grand Family raises their own regiments for defence, whilst the Commercial Court operates an elite mounted police.

In the wake of the Rebellions of the eighth century and general population growth, the younger members of many Optimate families are eyeing new acquisitions outside of the Rainside Mountains and Vales.

The Free Cities and Free Miners

Some cities and mining collectives treasure their free charters and make their own laws whilst still acknowledging the fundamental authority of the Administration and the basic laws, if not the power of any particular Senatorial family. Their existence is always on edge, with some failing and falling, and others wriggling out their freedom each decade.

The United Provinces Republic

The great grain fields of the Golden Riverlands were always a continuous issue for the Senatorial families, with many fighting to gain advantageous fiefdoms in the area. These conflicts, the need to boost production and the need to import the manufactured goods at high expense caused the peasants of the Riverlands to be treated abysmally. There was little recourse however until the great city of Angelsford rose up in riot after the Fingerthief serial killer was revealed to be the heir to the Brins family. After an ineffective and ill-judged attempt by the regiments to quell the rioters a revolutionary cabal seized control of the city. A levee en-mass of militia proved ill-suited to fight directly against the regiments, but it did have great success at enabling a vast peasant uprising all over the Riverlands, including the important furnace towns at the eastern edge of the Greatspire Mountains. Years and hundreds of thousands of death later the Army was a well-honed fighting machine, and the lines with the administration were stabilised (though a considerable amount of the area originally in revolt was lost).

Eventually the Northern Senatorial families tired of supporting the conflict (and had sufficiently propagandised and bribed their populace against the Republican ideas), and forced the Southern families to make peace with the Republic some century and a half ago.

Trade quickly resumed since the flow of food north and goods south were important to both economies, but tensions and occasional border clashes remain. With their freedom the Republic has gone full into a collectivist direct democracy with mandatory ten year service for all citizens. Some of the old religious have come to fore again and many speak out against all alterations to the baseline human form.

The Holy Sudlander Republic

Though initially remaining part of the Administrations territory after the Riverlands Rebellion, the lands south of the Colom mountains were now nearly impossible to administer, and broke away a few decades later in a shorter and less violent conflict. The Sudlanders have taken on the philosophical musings of the United Provinces with the enthusiasm of fanatics, and has begun persecution of all non-baseline humanity. Ironically even includes some natural features which are common on Terra and the original colonist stock but have become rare and exotic over the centuries like excessive paleness, red hair, or epicanthic folds. A systemic campaign against the Nighteyes and other Nomads of the Notreesland is currently being waged.

The Claw Pinnacle Autocracy

The only large state the Nighteyes dominate, the Autocrat of the Claw Pinnacle is an elected tyrant with decade long terms. Here the Nighteyes form settled agriculturalists in the hills, and the clear skies of the dayward portions of the claw mountains make them very suited for smelting via use of solar furnaces. An important stop on the Sky Guilds routes and the nomads of the Ghost plains, the decisions of the Autocrat have considerable weight with all the Nighteye population, even if their direct rule doen’t extend beyond the hills and the Bladecee.

Cissylvanian Republic

The main locus of non-Nighteyes peoples in the Windward side, the loose federation of the Cissylvanian republic is the great industrial power of Throl. The metals and constant sunlight of the Redspire Mountains allows vast smelting and casting operations, and Cissylvanian tools and guns can be found the world over. Extremely peaceful beyond the occasional nomad raid, the aggressive commercial and military intrusions of some Senatorial families (marching overland via the Skullands) is proving worrying to some of the Cissylvanians burgomasters. The old religions have been syncretized in Cissylvania to a surprising extent and tied in with a sun-worshiping sect that is making inroads in parts of the Administration and the UPR, whilst being banned by the Sudlanders.

The Sky Guild

The Sky Guild ply the vast land ocean of the eastern face of Throl, their huge airships sustained and powered by solar furnaces. Because of this they do not venture into the twilights or the Rainside, but their routes still encompass half of the planets surface. They have major holdings and trading stations in Cissylvania (where most of the airship components are made), Claw Pinnacle City, Seattell in the Colom Mountains, and various towns on the Arshwater, as well as rumoured secret cities in the Redspire Mountains. Blackened by the constant Sunshine, and self-selecting for Gifts related to spatial awareness and arboreal activities, they are on the verge of becoming their own ethnic grouping. Most of the trade in peoples, materials, and ideas between the Rainside and Windside runs via their hands, and they try to remain neutral in disputes.

Ghostrunner Nomads

Though acknowledging Claw pinnacles moral authority the Ghostrunner nomads have their own complex society based around their herds and mounts. When Grombrid rocks high they fish in the Lakes of Night, and when it falls low they ride out into the Green grass. Egalitarian to a fault there is little formal leadership amongst them though they are extremely vicious against other tribes and outsiders who look to consume their resources without asking (though they generously share with a traveller who does not touch without requesting). Full literacy has been maintained unlike some of the Silverblood tribes, via use of books printed in Claw Pinnacle, but their dialect has rapidly diverged from the basic English dialects the Administration still maintain across most of the planet.

Amazing worldbuilding! After reading about the specialized mount-beast Destriers I thought, "Hell yeah, Book of the New Sun." This would be an amazing world to read more about or see a new generation of sci-film set in. I sometimes fantasize about the sort of awesome things that would be produced if you and the other amazing sci-fi artists and worldbuilders around here formed a collective. Would kick the tail off of Avatar, I'm sure. I love it, man, great stuff.

Haha, yeah, I considered that around an hour after I left that message. In my enthusiasm I hadn't wholly taken that into account: you're definitely right there. The worlds you guys create independently are already mega-amazing in terms of spirit and scope.

A blend of 1700-1850s, with a few technologies that are much more sophisticated, there no coal or oil on the planet, so the only large scale power generation is via solar-thermal turbines and hydro-power (which have a limited geographic range where they can be employed). There is some cultural suppression of high energy technologies (to reduce their detect-ability in interstellar space), though if that's still required is a hotly debated point.